The invention relates to a valve structure for a sack or the like to be filled with air, which valve structure comprises an essentially cylindrical tubular part extending hermetically from the inside to the outside of the sack and having external threads on the portion outside the sack, a plug with internal threads to be screwed on the external threads of the tubular part to close the end of the tubular part hermetically, and a filling valve in the middle of the plug.
Especially at sea transports, air-filled stowage sacks are used to fill empty spaces between the cargo or between the cargo and the wall of the hold of the ship. A stowage sack prevents the cargo from moving in the hold and facilitates particularly the supporting of an unsymmetrical difficult cargo. The stowage sack is arranged in place empty and it is filled in its place, whereby it expands and adjusts itself to the form of the cargo. When unloading the cargo, the stowage sacks are emptied and removed from between the cargo.
For the use of stowage sacks, it is extremely important that the sacks can be filled and emptied quickly and easily. This is again influenced by the valve structure used in the first place. A prior art valve structure comprises a cylindrical mouthpiece hermetically inserted in a hole of a sack and provided with eternal threads. On this mouthpiece is screwed a plug provided with respective internal threads, which plug closes the end of the mouthpiece hermetically. In the middle of the plug, on its upper surface, is arranged a filling valve, through which the sack can be quickly filled with compressed air by using a special tool. After the sack has been filled, this valve is secured by arranging a special stopper therein. The air is removed from the sack by unscrewing the plug from the mouthpiece. Unscrewing the plug and especially screwing it back for refilling is, nevertheless, a difficult measure, particularly if the worker wears protective gloves. If the plug is not entirely removed from the mouthpiece, the air flows out between the plug and the mouthpiece, but too slowly, as far as the practical needs are concerned.